In a vane pump, pump chambers divided by vanes are expanded in a 180° section, one half of 360° rotation angle of a rotating portion, and are contracted in the remaining 180° section. A fluid is drawn from an inlet port in the pump chamber expanding section (hereinafter simply referred to as an “expanding section”). The fluid is discharged through an outlet port in the pump chamber contracting section (hereinafter simply referred to as a “contracting section”). In a conventional vane pump disclosed in Japanese Patent Laid-open Publication No. 9-42187 (JP9-42187A), an inlet port is provided in the substantially middle position of an expanding section. Furthermore, an outlet port is provided in the substantially middle position of a contracting section. A discharge path extends from the outlet port in the radially outward direction of a rotational axis.
If the inlet port is formed in the substantially middle position of the expanding section as set forth in JP9-42187A, it is sometimes the case that turbulence or vortex of a fluid is generated particularly in the chamber portion just ahead of the inlet port along the rotational direction, thus reducing the pump efficiency. In addition, if the discharge path is formed to extend radially outwards from the outlet port, it is sometimes difficult for the fluid to smoothly flow from each of the pump chambers toward the discharge path, consequently generating the turbulence or vortex of a fluid and reducing the pump efficiency.